Specialization and Trade-Offs in The Evolution of Resistance to Cheating in The Social Amoeba



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A central enigma of social evolution is the emergence and maintenance of cooperation and altruism in the face of selfish, free-loading individuals (i.e., cheaters), which take advantage of cooperators. One mechanism to counter cheating is the evolution of resistors. Both cheating and resistance appear to be persistent and prevalent in nature. However, whether resistance evolves to specifically outcompete local cheats, and whether it comes at the cost of reduced fitness in alternate environments is largely unknown. Here, I describe several experiments to: (i) test the cost of adaptation in replicate populations of social amoebae evolved in the presence of different cheaters, (ii) describe the function, transcriptomics, and population genomics of mutations identified in my evolved populations, and (iii) describe the population structure of the social amoeba at varying scales. Population structure analyses suggest significant differentiation in this species at spatial scales as small as one meter. Resistance readily evolved within each selection environment and strains performed better within their respective environments, revealing the capacity for cheating resistance with a variety of cheater in D. discoideum. I identified several genes mutated in the evolved strains that potentially influence resistance to cheating, and interestingly, that balancing selection might affect several of these genes. Trade-offs, thought to limit adaptation and drive specialization, were observed between selection groups. Thus, rapid adaptation in response to specific cheaters might prevent fixation of one cheater type in natural populations and might facilitate local adaptation of cheaters and resistors.



Evolution, Experimental evolution, Cheating, Amoeba, Dictyostelium, Population Structure, Population genetics, Whole Genome Sequencing